1. Technical Field
The present invention relates to an optical disk apparatus which has a sensing part fixed on a printed circuit board and which ensures a sufficient height for signal recognition with respect to an optical disk.
2. Description of the Related Art
The optical encoder is used in hard disks, compact disk players, and DVD players, etc., which is a sensor for measuring the number of rotations of a disk or hard disk, where a motor structure having such an optical encoder is illustrated in FIG. 1.
Referring to FIG. 1, the motor structure mainly comprises a disk 21, a motor providing rotational force to the disk 21, and an optical encoder detecting the rotation speed (rpm) of the disk 21.
The motor consists of a stator, which is fixed to a metal plate 11 and a printed circuit board 13 and which includes a metal bearing 27, a holder 29, and coils 33, and a rotor, which rotates together with the disk 21 and which includes a shaft 15, a rotation member 23, magnets 17, and a chuck 25, etc.
An electric current inputted from outside via the printed circuit board 13 is inputted to the coils 33, by which an electric field is generated around the coils 33. The interaction between the electric field thus generated and the magnetic field generated by the magnet 17 creates an electromagnetic force, which enables the rotor of the motor to rotate.
The holder 29 is fixed to the metal plate 11 and the printed circuit board 13, and the metal bearing 27 is inserted within the holder 29 to allow smoother rotation of the shaft 15. The shaft 15 rotates together with the disk 21 while supported by the holder 29 and the metal bearing 27, with the chuck 25 attached to the end of the shaft 15. The chuck 25 is of a structure that allows the mounting and demounting of the disk 21. Also, a sensor 19 capable of detecting the speed of the disk 21 is fixed onto the printed circuit board 13 by means of the holder 16.
Referring to FIG. 2, a conventional sensor 19 fixing device includes a holder 39 fixed onto a metal plate 11 by means of a screw 41, and a flexible printed circuit board 35 fixed onto the holder 39 by means of double-sided tape 37, etc. The flexible printed circuit board 35 is fixed to the printed circuit board 13 and the sensor 19 by means of solder 43. The sensor 19 is fixed to the flexible printed circuit board 35 by a reflow process.
A conventional sensor fixing device comprised as above is manufactured by the following process. First, the sensor 19 is fixed onto the flexible printed circuit board 35 by a reflow process. After fixing the flexible printed circuit board 35 onto the plastic holder 39 with double-sided tape 37, the sensor 19 and the flexible printed circuit board 35 are generally welded together. Then, after fixing the holder to the metal plate 11 using a screw 41, the printed circuit board 13 is fixed onto the metal plate 11 using double-sided tape 37, and the flexible printed circuit board 35 and the printed circuit board 13 are electrically connected using solder.
As shown above, a conventional sensor fixing device not only involves a relatively large number of components, as it requires double-sided tape 37 and the flexible printed circuit board 35, etc., but it also involves a large number of processes for joining each of the components. Thus, a conventional sensor fixing device entails complicated processes and high costs, and also incurs the problem of high defect rates.